Removal of Amoxicillin From Aqueous Solution in Batch and Circulated Fluidized Bed System Using Zinc Oxide Nanoparticles: Hydrodynamic and Mass Transfer Studies

Abstract

In this study pistachio shell waste coated with zinc oxide nanoparticles was investigated for its capacity to adsorb the antibiotic amoxicillin (AMO) from aqueous solutions. The pistachio shells, ZnO nanoparticles, and the prepared zinc oxide pistachio shell nanocomposite (CPS) were characterised using various techniques including Brunauer, Emmett and Teller, X-Ray Fluorescence, Fourier Transform Infrared Spectroscopy, Scanning Electron Microscope, and Energy Dispersive Spectroscopy. Batch and continuous flow system studies were carried out to study the adsorption behavior of CPS towards antibiotics. In the batch system, the factors affecting the sorption capacity of CPS including pH, contact time, initial AMO concentration, adsorbent dose, shaking speed, CPS particle size and temperature were investigated. The higher adsorption efficiency was reported at pH 5 for AMO at 70 mg/l initial AMO concentration with 150 rpm. The best adsorbent dose for above conditions was 0.08g/100 mL for AMO removal. The efficiency for removing AMO is affected by temperature and decreased with increasing temperature and is exothermic in nature. With increasing temp, negative value of ΔG° increase indicating that the adsorption process of AMO on CPS becomes unfavorable at higher temperatures. By the Langmuir model, the higher adsorption ability was 163 mg/g for AMO. The Pseudo-second order kinetic model very well simulated the kinetic experimental data and the adsorption rate parameters values indicating the removal process of AMO onto CPS was chemisorption and rate limiting contribute to the diffusion of the boundary layer, not intra-particular diffusion. A circulated fluidized bed reactor was adopted for the continuous removal of AMO, the influences of operating factors were studied including bed depth, air and water flow rate, and initial AMO concentration. The minimum fluidization velocity of bed was affected by Ug, dp, Hs and particle density. Different operating conditions were used, and the removal efficiency decreased when the liquid flow rate increased. Increasing air flow rate increase the time required for CPS to reach saturated. The obtained results show that CPS is an excellent medium for the adsorption of AMO from aqueous solution.